1/f noise study on strained Si0.8Ge0.2 p-channel MOSFETs with high-k/poly Si gate stack

The study of the low frequency (1/f) noise of strained Si0.8Ge0.2 p-channel MOSFETs with poly Si/HfSiOx gate stacks is presented. Apart from the reduced threshold voltage, improved maximum transconductance and increased low-field mobility offered by the strained SiGe, the 1/f noise was observed to be considerably lower than in the Si control devices. The 1/f noise characteristics were likely originated by carrier number fluctuations (Δn model) for both the strained SiGe and Si control pMOSFETs. This is consistent with the proposed model for high-k MOSFETs based on correlated number-mobility fluctuations theory. Despite the much worse high-k gate stack quality characterized by gate leakage and charge pumping, the relative reduction (up to 10×) in the noise for the strained SiGe over Si control with high-k is preserved, as was observed in the past for strained SiGe and Si control devices having SiO2 gate dielectric, likely attributed to the existence of the Si cap layer.